The invention relates to a device for timely signalling earthquakes or other movements of the ground. Thanks to its small size and low cost, it can be installed in any home, public or private office, in factories, cinemas, theatres and othr premises, and it is sufficiently sensitive to weak preshocks, which generally precede the large and destructive ones to act as a timely warning and permits therefore people to flee into the open or into other safe places.